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useful, there would be no more difficulty in preserving it in well-closed 
vessels than mauy others about which we have to be specially careful. 
I'he second alleged objection to plasma is, that it becomes mouldy by 
keeping. This statement is backed by the authority of names that command 
respect. Mr. Dean and Mr. Squire have both recorded this fact against 
plasma, and it is difficult to discredit anything advanced by observers of so 
large experience and of such well-known carefulness. But without intend¬ 
ing any contradiction of the observations of others, I am bound to assert that 
I never saw a particle of mould upon plasma, ^ind that since 1858 I have 
never been more than a few days at a time without plasma in stock. It is 
possible the mould to which these gentlemen refer may have appeared upon 
some of the compound plasmas. I admit I have not kept many of these for 
any length of time, but such as I have kept —Plasma Zinci and Plasma 
Petrolei—haxe remained as free from mould as simple plasma itself. I do 
not therefore feel disposed, as yet, to admit “a disposition to become mouldy 
by keeping” as a proved fact against plasmaj but, on the other hand, am 
bold to assert that it has but the one weak point already admitted. 
Though I have prepared plasma in batches varying from one ounce to 
twenty pounds, and have for experimental purposes occasionally modified 
my formula, I have found no advantage to result from any change, either in 
the proportions of the ingredients or in the selection of any particular starch- 
granule. Some experimentalists have supposed considerable differences in 
the results to have attended the employment of different feculas. My own 
experience goes rather to constrain me to attribute all variations of result to 
slightly altered manipulation. For instance, if, after heating the mixed in¬ 
gredients to the required temperature and for the required time, the vessel 
be removed from the fire and its contents allowed to cool without further 
stirring, they will become gelatinous and toughly elastic, a consistence very 
inconvenient for the required purpose; but by a little judicious stirring during 
the process of cooling this may be entirely obviated, and an excellent oint¬ 
ment-like consistence obtained. Again ; I have observed the translucency of 
the result to depend a good deal upon the time the mixture is exposed to 
heat, and the amount of stirring during the last part of the process. I find 
arrowroot, tqus-les-mois, and potato-starch will ail give equally good results 
under exactly similar circumstances ; and, on thq other hand, they all, under 
slightly modified circumstances, will yield inferior results. My experience, 
therefore, leads me to suggest but little change in my original instructions, 
which were as simple as could well be, viz.:—“ Take of starch powder 70 grs , 
glycerine 1 fl. oz, : mix the ingredients cold, and heat to 240°, constantly 
stirring.” All I would add to that is, if the batch be large, say 10 lb. or 201b., 
it is better to escape the dreary task of constantly stirring so large a mass, 
whilst it is being gradually heated to 240° (which must be done if the starch 
be added at the commencement of the process). This can be accomplished 
by mixing the starch with about one-twelfth of the glycerine, placing the 
remainder on the fire, and, when this has become heated to 260° (which will 
involve no special attention), mixing all together and stirring till complete. 
I venture then to repeat my opinion that plasma, carefully made, is a very 
elegant and useful material, possessing features of undoubted advantage over 
the fats commonly employed for ointments, and is not liable to any serious 
inconveniences. 
I wish now more particularly to refer to some of Dr. Bedwood’s remarks 
contained in his paper, “ On the Construction of a Pharmacopoeia ” (April 5, 
1865), and more especially to the nomenclature by which he proposes to 
designate this solid preparation of mine and a certain other class oifluid com¬ 
pounds of glycerine. He introduces the matter by a kindly and favourable 
mention of plasma. He says (vol. vi., 2nd series, p. 572);— 
